This invention relates to the preparation of perhydroacenaphthene useful as a high boiling oil by hydrogenating acenaphthene. More particularly, it relates to a process for selectively preparing cis-perhydroacenaphthene in pure form rather than as a mixture of isomers, which can be subsequently used as an intermediate for such chemical reaction as synthesis of adamantanes without incurring any difference in reaction route, activation energy, and reaction yield.
It is well known in the art to hydrogenate a polycyclic aromatic compound in an atmosphere of pressurized hydrogen in the presence of a noble metal-based catalyst such as Pt and Pd catalysts or a nickel-based catalyst such as Raney nickel and nickel/kieselguhr catalysts to eventually produce a corresponding perhydro compound.
For acenaphthene, it is well known that by hydrogenating acenaphthene in the presence of a Raney nickel catalyst, perhydroacenaphthene is produced by way of tetrahydroacenaphthene. As described in the literature (see J. Am. Chem. Soc., June 2, 1971, 2798), four stereoisomers are known for perhydroacenaphthene. The detail of these four isomers has not been generally investigated and no attempt has been made to selectively synthesize a particular isomer. Consequently, perhydroacenaphthene is usually available as a mixture of four isomers. It has never been attempted to selectively synthesize a particular isomer or a particular group of isomers.
No problem is encountered with an isomer mixture when perhydroacenaphthene is merely used as a high-boiling oil. It is, however, desirable to selectively synthesize a particular isomer or a particular group of isomers in using perhydroacenaphthene as an intermediate for chemical reaction to a final product because the reaction route and the activation energy involved in the reaction vary with isomers, resulting in varying reaction yields. As far as the literature and patent publications are concerned, no such concept about perhydroacenaphthene has been reported.
The Raney nickel used for hydrogenation requires a solvent for certain starting materials and is inconvenient because of short life and the need for careful handling.